Charon

Charon lune de Pluton

Charon, discovered by James Christy in 1978, is the largest satellite of the dwarf planet Pluto, not well known because of its remoteness, more than 7 billion miles. Charon is one of five satellites of Pluto with two other moons Nix and Hydra photographed with hubble telescope in 2005 and in 2012 a small moon named Kerberos and a fifth called Styx. The New Horizons mission is scheduled to visit Charon and Pluto in July 2015. Launched on 19 January 2006, will be the first spacecraft to visit Pluto. Charon is the largest satellite (1206 km diameter) compared to Pluto (diameter 2306 km). Charon has a mass about ten times lower than Pluto and the diameter ratio is from 1 to 2. The infernal couple rotates around its common center of gravity (centroid), as two connected by a rigid central bar as a dumbbell objects (see the simulation opposite).Charon is just 19,000 km from the dwarf planet moves around the planet with a period of 6.4 days, equal to the rotation period of Pluto, which is a synchronous orbit. It is by observing the occultation of the couple Pluto - Charon that scientists in 2005 were able to estimate the diameter of Charon is 1 207.2 ± 2.8 km (≈ 3 times smaller than our Moon).Charon as Pluto, has an inclined orientation relative to the plane of the ecliptic of about 17.1 ° and its eccentricity is approximately 0.24 orbit so that the orbit varies from 49.31 AU to 29.66 AU. The view of the orbits of Pluto-Charon and Neptune gives the impression that they intersect, but Pluto's orbit is tilted so that no part of the two orbits are close to one another. Pluto and Charon put 248 years to traverse the orbit, as the two objects pass in front of stars rich regions, it makes their observation difficult. Luckily, there are in the Milky Way a number of dark nebulae, regions where the concentration of interstellar dust hides the stars behind it. So we must wait patiently for the couple appears before a dark nebula.Nix and Hydra are two small satellites discovered orbiting Pluto, thanks to the Hubble Space Telescope in May and June 2005 by two American astronomers Alan Stern and Hal Weaver. The two new moons orbit at 44,000 miles from Pluto, twice as far as Charon. They measure between 45 and 160 km in diameter and 5000 times fainter than Charon. Both satellites circulate in the plane of Charon.

Charon is a distant goal for space exploration but the New Horizons probe, we learn a lot about this mysterious object.New Horizons is gone since 2006, received a gravity assist from Jupiter, its speed of 19 km / s, the fastest of all the probes ever launched by man. It will arrive as close to the couple at the summer of 2015, after traveling 6.4 billion kilometers. The observations will begin about five months before closest approach and should continue about a month later. The spacecraft will be carrying the imaging spectrometer and other instruments measuring devices to determine the geological and morphological characteristics of Pluto and Charon, but also map the components of the surface and study Pluto's atmosphere . The mission also provides an overview of the objects in the Kuiper belt until 2025.

Charon

characteristics

Discovered date

June 22, 1978

Discovered by

James W. Christy

Semi-major axisto system barycenter

17 536 ± 4 km

Semi-major axisto the center of Pluto

19 571 ± 4 km

Diameter

1 207 km ± 3 km

Mass

1.52×1021 kg

Surface area

4.58×106 km2

Gravity

0.278 m/s2

Escape velocity

0.58 km/s

Rotation

synchronous

Albedo

varies between 0.36and 0.39

Eccentricity

0.002 2

Orbital period

6.387 230 days6 d 9 h 17 m 36.7 s

Inclination to Pluto's equator

0.001°

Temperature

-220°C

Image: Charon, photography generated by computer from Hubble images taken in high resolution in October 2011. It comes mainly the hemisphere, making constantly face Pluto.

Image: Simulation of rotating two nearby objects like Pluto and Charon. The centroid or center of mass is located outside the main body.